React JS Suspense: Work Better with Async Data

ReactJS has been a game changer since it hit the scene in 2013. It’s user-friendly, has a ton of users, and is backed by a massive open-source community. Its popularity is off the charts and keeps climbing with every new feature and upgrade.

One of these features is ReactJS Suspense, which has been turning heads and wowing developers.

In this article, you’re going to learn what it does, how it works, and how it can take your React app’s performance and user experience to the next level. Let’s dive in.

React Suspense came out with React version 16.6. It lets you decide how your components should look while they’re waiting for data to load. You can control how your components render based on whether the data is ready or not.

Suspense allows you to “hold off” on showing a component until its data or code is loaded. In the meantime, you can show a placeholder component, like a loading spinner or a skeleton UI.

This helps you avoid showing the user an incomplete or inconsistent UI and can make your app feel faster and more responsive. React JS Suspense can work with any data fetching method, as long as it can throw a promise when the data isn’t ready yet.

Keep in mind, React JS Suspense isn’t a data-fetching library like Axios, or a state management library like Redux or Redux Toolkit. It’s a method that lets you express how your UI components depend on async data, and how to handle the loading state in a clear, declarative way.

One of the tricky parts of building apps is handling asynchronous network requests. It can be frustrating when there are delays, errors, and inconsistencies in the UI while data is being fetched from an API, a database, or a file. This can negatively affect the user experience and the performance of the app.

Before ReactJS Suspense came along, this fetched data was usually managed by third-party state management libraries like Redux. While using Redux and similar libraries has its benefits, the boilerplate and the data handling workflows across multiple modules or files can be long, complicated, and prone to errors.

React introduced Suspense to tackle this problem and offer a more streamlined way to handle asynchronous data during loading states.

Here’s how you can use ReactJS Suspense while data fetching:

1. You can use the <Suspense> component to wrap your components that rely on asynchronous data. You’ll need to provide a fallback prop that specifies what should be rendered while the data is loading.
2. Your data fetching logic should throw a promise when the data isn’t ready yet, and resolve it when the data becomes available. This way, ReactJS Suspense can handle the loading state for you.

Let's say you have a component that fetches and displays a list of tasks from an API. You can use ReactJS Suspense to handle the loading state of this component. Here’s how:

In this example, there’s a custom hook useTasks to fetch the data and store it in a state variable. If the state variable is null, you throw the promise returned by fetchTasks.

This suspends the rendering of the TaskList component.

The <Suspense> component then catches the promise and renders the fallback UI until the promise is resolved.

When the data is ready, the TaskList component resumes rendering and displays the list of tasks. Voila!

You can implement ReactJS Suspense to:

Show a Fallback UI

Showing a standby UI while data is loading up in the background makes things smoother for the user. It gives them a heads-up that something’s happening, keeps the layout from jumping around, and chills out any worries they might have.

Unveil Nested Component Progressively

The main part of the app shows up first, and the smaller parts come in as they get loaded up. This speeds up your app and keeps the screen from getting stuck.

Display Cached Content While Fresh Content Loads

The cached data sticks around until the new data comes in. This way, you avoid any loading screens and the screen doesn’t flicker.

Related: How to Clear DNS Cache on Chrome with chrome.//net-internals/#dns

Signal a Transition

You can pop up a special transition screen when the user moves around or does something that needs fresh data or code. This makes it clear what’s going on and cuts down on any mix-ups.

Offer a Fallback For Server Errors and Client-Only Content

You can also handle situations where pulling in the data doesn’t work out or the data’s gone missing on the server. This keeps your app from crashing and shows a fitting error message or a standby screen.

Using Suspense in React packs several benefits for you to improve the user experience and performance of your React app. Here are some of them:

Declarative and Consistent Loading States

ReactJS Suspense lets you specify the loading state of your components in a declarative way, without having to use conditional rendering or state variables.

It also ensures that the loading state is consistent across the component tree, by rendering the fallback UI only when the data is not available for all the components in the Suspense boundary.

Seamless Transitions and Animations

ReactJS Suspense allows you to control the timing and sequencing of your component transitions.

You can specify how long to wait before showing the fallback UI, and how long to keep showing the fallback UI after the data is ready. This way, you can avoid showing unnecessary spinners or flashes of content, and create smooth and seamless transitions and animations for your components.

Error Handling and Retry Logic

ReactJS Suspense also provides a way to handle errors and retry logic for your data fetching components, by using the <ErrorBoundary> component. The <ErrorBoundary> component is similar to the <Suspense> component, but it catches errors instead of promises and renders a fallback UI that can display an error message or a retry button.

You can also use the <ErrorBoundary> component to wrap your <Suspense> component and handle any errors that may occur during data fetching.

Concurrent Mode Compatibility

ReactJS Suspense is developed to work with the concurrent mode of React, which is a new experimental feature that enables React to render your components in a non-blocking way and prioritize the updates that are most important for the user experience.

Suspense integrates with the concurrent mode and allows you to take advantage of its features, such as time slicing, batching, and selective hydration.

Time slicing, batching, and selective hydration are some of the features that ReactJS offers to improve the performance and user experience of web apps. Here’s a brief explanation for each:

• Time slicing: React breaks rendering into small pieces and does them when idle, without blocking the main thread or user input.
• Batching: React combines multiple state updates into one render, saving re-rendering and making the app faster.
• Selective hydration: React hydrates (links HTML to JavaScript) the most critical parts of the app first, and delays or skips the rest.